Wicking nonwoven mat from wet-laid process

ABSTRACT

Examples of the present technology may include a method of making a non-woven fiber mat. The wet nonwoven fiber mat may include a first plurality of first glass fibers and a second plurality of second glass fibers. The first plurality of first glass fibers may have nominal diameters of less than 5 μm, and the second plurality of second glass fibers may have nominal diameters of greater than 6 μm. The method may further include curing the binder composition to produce the nonwoven fiber mat. The nonwoven fiber mat may have an average 40 wt. % sulfuric acid wick height of between about 1 cm and about 5 cm after exposure to 40 wt. % sulfuric acid for 10 minutes conducted according to method ISO8787, and the nonwoven fiber mat may have a total normalized tensile strength greater than 2 (lbf/in)/(lb/sq) for a sq (100 ft 2 ).

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is related to U.S. patent application Ser. No.14/642,361, entitled “SMALL PORE SIZE NONWOVEN MAT WITH HYDROPHILIC/ACIDRESISTANT FILLER USED IN LEAD ACID BATTERIES AND APPLICATIONS THEREFOR,”to Guo et al. filed on Mar. 9, 2015, the entire contents of which areincorporated by reference herein.

BACKGROUND

Electrodes or electrode plates commonly used in lead-acid batteriesoften include a metallic grid that is used to support lead and/or leadoxide pastes. During charge and discharge cycles, the volume of the leadand/or lead oxide paste typically expands and contracts. Repeated usageand, thus, repeated charge and discharge cycles may have negativeeffects on the electrode, such as shedding of the active materialparticles of the lead and/or lead oxide pastes. To reduce those negativeeffects, the electrodes may be reinforced with paper to keep the lead orlead oxide paste intact. These papers also may have the advantage ofwicking electrolyte along the electrode plates. This wicking may helpbattery performance. These pasting papers in the battery should haveadequate wickability and tensile strength, including in the harshchemical environment within the battery. These and other characteristicsand improvements of pasting papers are addressed.

BRIEF SUMMARY

Processing methods, batteries, nonwoven fiber mats, and pasting papersmay involve a greater fraction of coarse fibers than microfibers. Thismixture of fibers, along with a binder composition, may be made into anonwoven fiber mat with adequate wickability properties in batteries andsuperior mechanical strength characteristics. The superior strengthcharacteristics may provide for more support for the electrode platesfor AGM (Absorptive Glass Mat) batteries and for more robust batteries.The increased strength also may improve process efficiency and mayreduce scrapping during battery manufacture. Wickability may be enhancedby adding a filler. Without a high concentration of microfibers, methodsof manufacturing nonwoven fiber mats may not need acidic conditions todisperse microfibers. Without low pHs, processing equipment may notrequire stainless steel or other expensive materials. Additionally, therelative ease of dispersing and mixing fibers may allow for processes tobe run continuously and without interruption, which may result indecreased costs and increased throughput.

Examples of the present technology may include a method of making anon-woven fiber mat for use in a lead-acid battery. The method mayinclude adding a binder composition to a wet nonwoven fiber mat. The wetnonwoven fiber mat may include a first plurality of first glass fibersand a second plurality of second glass fibers. The first plurality offirst glass fibers may have nominal diameters of less than 5 μm, and thesecond plurality of second glass fibers may have nominal diameters ofgreater than 6 μm. The first plurality of first glass fibers may have aweight between about 10% and about 50% of the combined weight of thefirst plurality of first glass fibers and the second plurality of secondglass fibers. The method may further include curing the bindercomposition to produce the nonwoven fiber mat. The nonwoven fiber matmay have an average 40 wt. % sulfuric acid wick height of between about1 cm and about 5 cm after exposure to 40 wt. % sulfuric acid for 10minutes conducted according to method ISO8787, and the nonwoven fibermat may have a total normalized tensile strength greater than 2(lbf/in)/(lb/sq) for a sq of 100 ft². The normalized tensile strength isderived from the sum of the average machine direction tensile strength(lbf/in) and the average cross machine direction tensile strength(lbf/in), divided by the mat weight (lb/sq).

These or other examples of the present technology may include alead-acid battery. The battery may include a positive electrode, anegative electrode, and a nonwoven fiber mat disposed adjacent thepositive electrode or the negative electrode. The nonwoven fiber matinclude a first plurality of first glass fibers having nominal diametersof less than 5 μm. The nonwoven fiber mat may further include a secondplurality of second glass fibers having nominal diameters greater than 6μm. The first plurality of first glass fibers may make up between about10% and about 50% by weight of the combined weight of the firstplurality of first glass fibers and the second plurality of second glassfibers. The nonwoven fiber mat may also include a binder composition.The nonwoven fiber mat may have an average 40 wt. % sulfuric acid wickheight of between about 1 cm and about 5 cm after exposure to 40 wt. %sulfuric acid for 10 minutes conducted according to method ISO8787,while the nonwoven fiber mat may have a total normalized tensilestrength of greater than 2 (lbf/in)/(lb/sq).

Some examples of the present technology may include a method of making apasting paper for battery. The method may include applying anacid-resistant binder composition to a wet-laid mixture of glass fibersto form a wet nonwoven fiber mat. The mixture of glass fibers mayinclude a first plurality of microfibers having an average diameter ofbetween 0.5 μm and 1.0 μm and a second plurality of coarse fibers havingan average diameter greater than or equal to 8 μm. The mass ratio of thefirst plurality of microfibers to the second plurality of coarse fibersmay be between about 1:5 and about 1:1. The method may further includedrying the wet nonwoven fiber mat. The method may also include curingthe acid-resistant binder composition to produce a pasting paper. Thepasting paper may have an average 40 wt. % sulfuric acid wick height ofbetween about 1 cm and about 5 cm after exposure to 40 wt. % sulfuricacid for 10 minutes conducted according to method ISO8787. In addition,pasting paper may have a total normalized tensile strength of greaterthan 7 (lbf/in)/(lb/sq).

Additional examples and features are set forth in part in thedescription that follows, and in part will become apparent to thoseskilled in the art upon examination of the specification or may belearned by the practice of the invention. The features and advantages ofthe invention may be realized and attained by means of theinstrumentalities, combinations, and methods described in thespecification.

BRIEF DESCRIPTION OF THE DRAWINGS

The present technology is described in conjunction with the appendedfigures:

FIG. 1 illustrates an exploded perspective view of a battery cellassembly;

FIG. 2 illustrates an assembled cross section view of the battery cellassembly of FIG. 1;

FIGS. 3A-3C illustrate cross section views of various configurations ofan electrode or plate and a nonwoven fiber mat;

FIG. 4 illustrates a process for preparing an electrode or plate havinga nonwoven fiber mat disposed on or near a surface of the electrode orplate;

FIG. 5 shows a block diagram of a method of making a nonwoven fiber mat;and

FIG. 6 shows a block diagram of a method of making a pasting paper.

DETAILED DESCRIPTION

Conventional pasting papers for AGM batteries may be structurally weak.A majority of the fibers in the conventional pasting papers may bemicrofiber glass. The nonwoven fiber mat may have high wickingproperties, above what is needed for lead-acid batteries and otherapplications. A wickable nonwoven fiber mat in a battery may helpmaintain electrolyte or other liquid coverage of electrode plates, butlittle, if any, data exist to support the high level of wickability inconventional nonwoven fiber mats. This overdesigned wickabilitycharacteristic may be the result of a higher concentration ofmicrofibers relative to coarse fibers. An increased concentration ofmicrofibers compared to coarse fibers may result in a nonwoven fiber matwith decreased mechanical strength, which may result from the lowerindividual mechanical strength of smaller diameter fibers.

Additionally, conventional processes, which may include specialty papermachines, of making nonwoven fiber mats for batteries and otherapplications may be more expensive and/or have lower throughput. Thehigher concentration of microfibers, which are generally more expensivethan coarse fibers, may increase material cost. Acids may often be usedto disperse microfibers to create a uniform mixture of microfibers andcoarse fibers. The low pHs (usually less than 3) may be corrosive, andthe process may require equipment made from stainless steel or otherexpensive materials. Because of the challenge in dispersing microfibers,conventional processes may be run in batch or semi-batch operations,instead of continuous operations, to ensure a sufficiently uniformmixture of fibers. A semi-batch operation may include using a first tankin the process while mixing fibers in a second tank, and then switchingthe process to the second tank while mixing fibers in the first tank.For these and other reasons, materials and methods used in conventionalnonwoven fiber mat and battery technologies may not be cost effective orefficient.

FIGS. 1 and 2, respectively, show a perspective exploded view of alead-acid battery cell 200 and a cross-section assembled view of thelead-acid battery cell 200. The lead-acid battery cell 200 may representa cell used in either flooded lead-acid batteries or Absorptive GlassMat (AGM) batteries. Each cell 200 may provide an electromotive force(emf) of about 2.1 volts and a lead-acid battery may include 3 suchcells 200 connected in series to provide an emf of about 6.3 volts ormay include 6 such cells 200 connected in series to provide an emf ofabout 12.6 volts, and the like. Cell 200 may include a positive plate orelectrode 202 and a negative plate or electrode 212 separated by batteryseparator 220 so as to electrically insulate the electrodes 202 and 212.Positive electrode 202 may include a grid or conductor 206 of lead alloymaterial. A positive active material 204, such as lead dioxide, maytypically be coated or pasted on grid 206. Grid 206 may also beelectrically coupled with a positive terminal 208. Grid 206 may providestructural support for the positive active material 204 along withelectrical conductivity to terminal 208.

Likewise, negative electrode 212 may include a grid or conductor 216 oflead alloy material that is coated or pasted with a negative activematerial 214, such as lead. Grid 216 may be electrically coupled with anegative terminal 218. Like grid 206, grid 216 structurally may supportthe negative active material 214 along with providing electricalconductance to terminal 218. In flooded type lead-acid batteries,positive electrode 202 and negative electrode 212 may be immersed in anelectrolyte (not shown) that may include a sulfuric acid and watersolution. In AGM type lead-acid batteries, the electrolyte may beabsorbed and maintained within battery separator 220. Battery separator220 may be positioned between positive electrode 202 and negativeelectrode 212 to physically separate the two electrodes while enablingionic transport, thus completing a circuit and allowing an electroniccurrent to flow between positive terminal 208 and negative terminal 218.Separator 220 may not include the fibers of the reinforcement mats.Separator 220 may include a microporous membrane (i.e., the solid blackcomponent), which is often a polymeric film having negligibleconductance. The polymeric film may include micro-sized voids that allowionic transport (i.e., transport of ionic charge carriers) acrossseparator 220. In some examples, the microporous membrane or polymericfilm may have a thickness of 50 micrometers or less, including 25micrometers or less, may have a porosity of about 50% or 40% or less,and may have an average pore size of 5 micrometers or less, including 1μm or less. The polymeric film may include various types of polymersincluding polyolefins, polyvinylidene fluoride, polytetrafluoroethylene,polyamide, polyvinyl alcohol, polyester, polyvinyl chloride, nylon,polyethylene terephthalate, and the like. Separator 220 may also includeone or more fiber mats that are positioned adjacent one or both sides ofthe microporous membrane/polymeric film to reinforce the microporousmembrane and/or provide puncture resistance.

Positioned near a surface of negative electrode 212 may be a nonwovenfiber mat 230 (referred to herein as a reinforcement mat). Reinforcementmat 230 may be disposed partially or fully over the surface of negativeelectrode 212 so as to partially or fully cover the surface. As shown inFIG. 2, a reinforcement mat 230 may be disposed on both surfaces of thenegative electrode 212, or may fully envelope or surround the electrode.Likewise, although reinforcement mat 230 is shown on the outer surfaceof the electrode 212, in some examples, reinforcement mat 230 may bepositioned on the inner surface of the electrode 212 (i.e., adjacentseparator 220). Reinforcement mat 230 may reinforce the negativeelectrode 212 and may provide an additional supporting component for thenegative active material 214. The additional support provided byreinforcement mat 230 may help reduce the negative effects of sheddingof the negative active material particles as the active material layersoftens from repeated charge and discharge cycles. This may reduce thedegradation commonly experienced by repeated usage of lead-acidbatteries.

Reinforcement mat 230 may often be impregnated or saturated with thenegative active material 214 so that the reinforcement mat 230 ispartially or fully disposed within the active material 214 layer.Impregnation or saturation of the active material within thereinforcement mat means that the active material penetrates at leastpartially into the mat. For example, reinforcement mat 230 may be fullyimpregnated with the negative active material 214 so that reinforcementmat 230 is fully buried within the negative active material 214 (i.e.,fully buried within the lead paste). Fully burying the reinforcement mat230 within the negative active material 214 means that the mat isentirely disposed within the negative active material 214. In examples,reinforcement mat 230 may be disposed within the negative activematerial 214 up to about a depth X of about 20 mils (i.e., 0.020 inches)from an outer surface of the electrode 212. In other examples, the glassmat 230 may rest atop the negative active material 214 so that the matis impregnated with very little active material. Often the reinforcementmat 230 may be impregnated with the negative active material 214 so thatthe outer surface of the mat forms or is substantially adjacent theouter surface of the electrode 212 (see reinforcement mat 240). In otherwords, the active material may fully penetrate through the reinforcementmat 230 so that the outer surface of the electrode 212 is a blend ormesh of active material and reinforcement mat fibers.

The thickness of the glass mat may be a function of mat weight, bindercontent (Loss on Ignition [LOI]), and fiber diameter. The type of binderused and the length of the fibers may be weaker factors in determiningthe glass mat thickness. Higher binder content, however, may generallyreduce the glass mat thickness, although excessive binder use may posevarious processing challenges during mat production and thereafter. Alower mat weight may also reduce the mat thickness. The mat weight,however, may also be limited because the mat needs to provide enoughtensile strength during winding and downstream processes.

As described herein, reinforcement mat 230 may include a plurality ofglass fibers and an acid resistant binder that couples the plurality ofglass fibers together to form the reinforcement mat. Reinforcement mat230 may have an area weight of between about 10 and 100 g/m², includingbetween about 20 and 60 g/m². Reinforcement mat 230 may be used forreinforcing a plate or electrode of a lead-acid battery and may includea relatively homogenous mixture of coarse glass fibers that may includea plurality of first glass fibers having a diameter between about 0.5-5μm and a plurality of second fibers having a diameter of at least 6 μm.Relatively homogenous may mean that the mixture is at least 85%homogenous. In some examples the relatively homogenous mixture may makeup between about 70-95% of the mass of the mat 230. In some examples,the homogenous mixture may also include 5-30% conductive fibers. Forexample, conductive fibers having diameters about 6 μm and above andhaving lengths between about 8 and 10 mm can be included in therelatively homogenous mixture. The reinforcement mat 230 also includesan acid resistant binder that bonds the plurality of first and secondglass fibers together to form the reinforcement mat 230. Thereinforcement mat 230 further includes a wetting component that isapplied to reinforcement mat 230 to increase the wettability/wickabilityof the reinforcement mat 230. The wettability/wickability of thereinforcement mat 230 may be increased such that the reinforcement mat230 has or exhibits an average 40 wt. % sulfuric acid wick height and/orwater/acid solution wick height of at least 1.0 cm after exposure to therespective solution for 10 minutes in accordance with a test conductedaccording to method ISO8787.

Examples of the present technology may include coarse glass fibers andglass microfibers homogeneously dispersed throughout the nonwoven glassmat. These nonwoven glass mats may not involve a simple integration ofparts or components. Instead, producing a nonwoven glass mat with coarseglass fibers in a wet laid process may require one set of parametersthat are vastly different than the parameters that are used to produce anonwoven glass mat with microfibers. In fact, many manufacturingparameters may be adjusted to produce a homogenous nonwoven glass mat. Ahomogenous nonwoven glass mat may provide benefits over layeredconstruction. In layered construction, coarse fibers may tend to form abottom layer and microfibers may form a layer on top of the bottomlayer. Unlike a layered construction mat, a homogenous mat may haveuniform resistance across the mat and may result in uniform current andutilization of active materials.

Reinforcement mat 230 may include a conductive material so as to makereinforcement mat 230 electrically conductive. For example, a conductivelayer may be formed on one or more sides of reinforcement mat 230 byapplying a conductive material to at least one surface of reinforcementmat 230 or throughout reinforcement mat 230. The conductive layer may bepositioned to face and contact electrode 212 to provide electricalpathways along which the electrons may flow. The conductive materialcontacts the electrode 212, and more specifically the active material ofelectrode 212 to enable electron flow on a surface or throughreinforcement mat 230. In some examples, the conductive layer ofreinforcement mat 230 may be electrically coupled with a negativeterminal 218 to provide a route or path for current flow to terminal218. Conductive material is described in U.S. patent application Ser.No. 14/489,093 filed Sep. 17, 2014, which is incorporated herein byreference for all purposes.

As briefly described above, reinforcement mat 230 may include aplurality of electrically insulative fibers, such as glass, polyolefin,polyester, and the like, which are primarily used to reinforce theelectrode. Because the reinforcement mat 230 may be made of suchinsulative fibers, the reinforcement mat 230 may be essentiallynon-conductive prior to or without the addition of the conductivematerial. For example, without combining or adding the conductivematerial/layer, the reinforcement mat 230 may have an electricalresistance greater than about 1 Megaohm per square. In manufacturing thereinforcement mat 230, water or another liquid may be removed (e.g., viaa vacuum) from a suspension of the fibers in the liquid medium. A bindermay then be applied to the wet-laid non-woven glass or polyolefin fibersto form reinforcement mat 230. As described previously, in someexamples, the conductive material or fibers may be added to the binderand/or to the liquid medium. As an example, reinforcement mat 230 mayhave a thickness of between about 50 μm and about 500 μm and have anaverage pore size of between about 5 μm and about 5 millimeters.

The reinforcement mat 230 also may include a wetting component that isapplied to the reinforcement mat to increase the wettability/wickabilityof the reinforcement mat. The wettability/wickability of thereinforcement mat 230 may be increased so that the reinforcement mat hasor exhibits an average water wick height and/or average water/acidsolution wick height of at least 0.5 cm after exposure to the respectivesolution for 10 minutes in accordance with a test conducted according tomethod ISO8787. The mat may exhibit an average water/acid solution wickheight of at least 0.5 cm without an additional wetting component.

As described herein, the wetting component may be a wettable componentof the acid resistant binder (e.g., a hydrophilic functional group), ahydrophilic binder that is mixed with the acid resistant binder, thewetting component may be component fibers (e.g., cellulose, cotton,other natural fibers, polyester, other synthetic fibers, or acombination of natural and/or synthetic fibers) that are bonded with theglass fibers of the reinforcement mat 230, or the wetting component maybe a wettable solution (e.g., starch or cellulose solution) that isapplied to the reinforcement mat 230 such that the wettable solutionsaturates the reinforcement mat 230 or is disposed on at least onesurface of the reinforcement mat 230 upon drying of the wettablesolution. In some examples, the wetting component may include acombination of any of the aforementioned components, such as acombination of cellulose fibers and an acid resistant binder having awettable component. In specific examples, the glass fibers ofreinforcement mat 230 may include first fibers having fiber diametersbetween about 0.5 μm and about 5 μm or between about 0.5 μm and about 1μm and second fibers having fiber diameters of at least about 6 μm.According to some examples, the component fibers may form a componentfiber mat that is bonded to at least one side of the glass reinforcementmat 230 such that the reinforcement mat 230 comprises a two layer matconfiguration. The component fibers may be mixed with the glass fiberssuch that upon forming the glass mat the component fibers may beentangled with and bonded to the glass fibers.

Referring now to FIGS. 3A-3C, illustrated are variouselectrode-reinforcement mat configurations. FIG. 3A illustrates aconfiguration where an electrode 300 has a single reinforcement mat 302disposed on or near an outer surface. As described above, reinforcementmat 302 may include a conductive material and/or layer so as to enableelectron flow on a surface and/or through reinforcement mat 302 to abattery terminal. Reinforcement mat 302 may also include a wettingcomponent as described above to provide the mat 302 with enhancedwettability characteristics. Reinforcement mat 302 may partially orfully cover the outer surface of electrode 300. The configuration ofFIG. 3B may be similar to that of FIG. 3A except that an additionalreinforcement mat 304 may be disposed on or near an opposite surface ofelectrode 300 so that electrode 300 may be sandwiched between the twoglass mats, 302 and 304. FIG. 3C illustrates a configuration where areinforcement mat 306 may envelop or surround electrode 300. AlthoughFIG. 3C illustrates the reinforcement mat 306 fully enveloping theelectrode 300, in many examples a top side or portion of the mat 306, ora portion thereof, is open.

Referring back to FIGS. 1 and 2, positioned near a surface of positiveelectrode 202 is a reinforcement mat 240. Reinforcement mat 240 may bearranged and/or coupled with positive electrode 202 similar to thearrangement and coupling of reinforcement mat 230 with respect tonegative electrode 212. For example, reinforcement mat 240 may bedisposed partially or fully over the surface of positive electrode 202so as to partially or fully cover the surface, may be positioned on aninner surface of the electrode 202 (i.e., adjacent separator 220)instead of the shown outer surface configuration, and/or may beimpregnated or saturated with the positive active material 204 so thatthe reinforcement mat 240 is partially or fully disposed within theactive material 204 layer. Like reinforcement mat 230, reinforcement mat240 may provide additional support to help reduce the negative effectsof shedding of the positive active material particles due to repeatedcharge and discharge cycles.

Regarding the reinforcement functions of reinforcement mats 230 and/or240, in some examples the reinforcing aspects of these mats may beenhanced by blending fibers having different fiber diameters.Reinforcement mats 230 and 240 (referred to hereinafter as reinforcementmat 230) can have similar characteristics and compositions, and caninclude a blend of two or more different diameter fibers. Reinforcementmat 230 includes a plurality of first microfibers, having fiberdiameters ranging between about 0.5 μm and about 5 μm, between about 0.5μm and about 1 μm, or between about 0.7 μm and about 2 μm. The firstmicrofibers are blended with a plurality of second coarse fibers, havingfiber diameters of at least about 6 μm, including between about 8 μm andabout 13 μm. In some examples, the plurality of second coarse fibers mayinclude a silane material sizing. The blend of the two or more differentdiameter fibers results in a mat that is sufficiently strong tostructurally support the active material as described above and towithstand the various plate manufacturing processes while alsominimizing the thickness and overall size of the mat. Reducing thethickness of reinforcement mat 230 while maintaining mat strength may bedesired since reinforcement mat 230 typically is a chemically inactivecomponent and, thus, does not contribute to the battery'selectrochemical process. Reducing the volume of reinforcement mat 230helps minimize the battery's volume of non-electrochemicallycontributing components.

In examples, reinforcement mat 230 includes a blend of between 10% and50% of the first microfibers and between 50% and 85% of the secondcoarse fibers. In these or other examples, reinforcement mat 230 mayinclude a blend of between 20% and 30% of the first microfibers andbetween 70% and 80% of the second coarse fibers. In these or otherexamples, reinforcement mat 230 may include a blend of between 30% and50% of the first microfibers and between 50% and 70% of the secondcoarse fibers. In some examples, reinforcement mat 230 may include ablend of between 10% and 40% of the first microfibers and between 60%and 85% of the second coarse fibers. In yet other examples, the blend offirst microfibers and second coarse fibers is approximately equal (i.e.,50% of the first microfibers and second coarse fibers).

The length of the coarse fibers may also contribute to the overallstrength of reinforcement mat 230 by physically entangling with adjacentfibers or fiber bundles and/or creating additional contact points whereseparate fibers are bonded via an applied binder. In examples, thecoarse fibers have fiber lengths that range between about ⅓ inch andabout 1½ inches, although an upper length limit of 1¼ inch is morecommon. This range of lengths provides sufficient mat strength whileallowing the fibers to be dispersed in a white water solution for matprocessing applications. In other examples, the coarse fibers have fiberlengths that range between ½ and ¾ of an inch. The fibers lengths of thefirst microfibers may be different than the fibers lengths of the secondcoarse fibers.

The type and amount of binder used to bond the first microfiber andsecond coarse fibers together may also contribute to the overallstrength and thickness of reinforcement mat 230. As described above, thebinder is generally an acid and/or chemically-resistant binder thatdelivers the durability to survive in the acid environment throughoutthe life of the battery, the strength to survive the plate pastingoperation, and the permeability to enable paste penetration. Forexample, the binder may be an acrylic binder, a melamine binder, a UFbinder, or the like. The binder may also include and bond the conductivematerial to the first and/or second coarse fibers. Increased binderusage may reduce the thickness of reinforcement mat 230 by creating morefiber bonds and densifying reinforcement mat 230. Increased fibers bondsmay also strengthen reinforcement mat 230. In examples, the binder isapplied to the first microfibers and second coarse fibers such that thebinder includes between about 5% and 45% by weight of the reinforcementmat 230 or between about 10% and 35% by weight of the reinforcement mat.In some examples, the binder is applied to the first microfibers andsecond coarse fibers such that it includes between about 5% and 30% byweight of the reinforcement mat 230.

The wetting component may be mixed with the binder in some examples. Theresulting reinforcement mat 230 may have or exhibit an average 40 wt. %sulfuric acid wick height of at least 0.5 cm after exposure to 40 wt. %sulfuric acid for 10 minutes conducted according to method ISO8787. Thewetting component may be dissolvable in an acid solution of thelead-acid battery such that a significant portion of the nonwoven fibermat is lost due to dissolving of the wetting component. For example,between about 5-85% of the mass of the reinforcement mat 230 may belost.

In some examples, reinforcement mat 250 may also include a conductivematerial and/or layer to enable electron flow on a surface and/orthrough reinforcement mat 250 to positive terminal 208 and/or negativeterminal 218.

In some examples, reinforcement mat 250 may also include a wettingcomponent. For example, reinforcement mat 250 may include 10-40% ofcotton fibers, such as cotton microfibers having diameters of betweenabout 0.5 and 3.0 μm. The wetting component may increase thewettability/wickability of the reinforcement mat 250 such that thereinforcement mat 250 has or exhibits an average water wick heightand/or water/acid solution wick height of at least 1.0 cm after exposureto the respective solution for 10 minutes in accordance with a testconducted according to method ISO8787. The wickability of thereinforcement map may reach the same wickability without the addition ofa wetting component. Reinforcement mat 250 may be called a separatorsupport and may include any of the compositions described forreinforcement mat 230.

Referring now to FIG. 4, illustrated is a process 400 for manufacturingan electrode. The process may involve transporting a lead alloy grid 410on a conveyor toward an active material 430 applicator (e.g., lead orlead oxide paste applicator), which applies or pastes the activematerial 430 to the grid 410. A nonwoven mat roll 420 may be positionedbelow grid 410 so that a reinforcement mat is applied to a bottomsurface of the grid 410. The reinforcement mat may include a conductivematerial and/or layer, as well as a wetting component, as describedherein. In some examples, the reinforcement mat may also include a blendof fibers as described herein. In some examples, the reinforcement matmay also include a blend of coarse fibers and microfibers in addition tothe wetting component as described herein. A second nonwoven mat roll440 may be positioned above grid 410 so that a second reinforcement matis applied to a top surface of the grid 410. The second reinforcementmat may also include a conductive material, a wetting component, and/orlayer and/or blend of coarse fibers and/or microfibers (similar to ordifferent from reinforcement mat 420). The resulting electrode or plate450 may subsequently be cut to length via a plate cutter (not shown). Asdescribed herein, the active material 430 may be applied to the grid 410and/or top and bottom of reinforcement mats, 440 and 420, so that theactive material impregnates or saturates the mats to a desired degree.The electrode or plate 450 may then be dried via a dryer (not shown) orother component of process 400. As described herein, the reinforcementmats, 440 and 420, may aid in the drying of the electrode or plate 450by wicking the water and/or water/acid solution from the electrode orplate 450 so as to allow the water and/or water/acid solution toevaporate.

Examples of the present technology may include a method of making anon-woven fiber mat for use in a lead-acid battery. FIG. 5 shows amethod 500 of making a non-woven fiber mat. Method 500 may includeadding a binder composition to a wet nonwoven fiber mat 502. The wetnonwoven fiber mat may include a first plurality of first glass fibersand a second plurality of second glass fibers. The first plurality offirst glass fibers may have nominal diameters of less than 5 μm, betweenabout 0.5 μm and about 1.0 μm, or about 0.7 μm, for example. The secondplurality of second glass fibers may have nominal diameters of greaterthan 6 μm. For example, the second glass fibers may have averagediameters of between about 8 μm and about 13 μm, between about 8 μm andabout 10 μm, or between about 11 μm and 13 μm. The first plurality offirst glass fibers may have a weight between about 10% and about 50%,between about 30% and about 40%, between about 40% and about 50%,between about 20% and about 30%, between about 10% and about 20%, orbetween about 15% and about 30% of the combined weight of the firstplurality of first glass fibers and the second plurality of second glassfibers. While conventional nonwoven fiber mats for batteries may includemore microfiber than coarse fiber, methods described herein with morecoarse fiber than microfiber may produce a nonwoven fiber mat withincreased mechanical strength. The mat's increased mechanical strengthmay accompany a decreased, though still sufficient, wickability.

The first glass fibers may include a first glass composition, and thesecond glass fibers may include a second glass composition, where thefirst glass composition is different from the second glass composition.For example, different glass compositions include compositions withalumina, sodium oxide, silicon dioxide, magnesium oxide, calcium oxide,or other compounds. The first glass composition may be the same ordifferent as the second glass composition.

Method 500 may include a wet laid process and/or may exclude aconventional paper-making process. Glass fiber may be added to a whitewater (also called process water). The fiber may be dispersed in thewhite water using a pulper to form a slurry. In the slurry, the fibermay have a concentration of 0.2-1.0 wt. %. The method may furtherinclude maintaining a pH of the slurry at about 5 or higher. The pH ofthe slurry may be non-acidic or from neutral to slightly basic. Forexample, the pH of the slurry may be maintained between about 7 andabout 8.5. Without a high concentration of smaller diameter fibers, acidor acidic conditions may not be needed to increase the dispersion ofthese smaller diameter fibers. Reducing or eliminating the acid neededmay possess certain processing advantages. The slurry may be mixed withadditional white water and then deposited onto a moving screen. Themoving screen may be a forming belt. The screen may dewater the slurry,which may form the wet nonwoven fibrous mat.

The wet nonwoven mat of glass fiber may be transferred to a secondmoving screen and run through a binder application saturating station.The second moving screen may be called a binder application belt. In thebinder application saturating station, an aqueous binder mixture, suchas an acrylic binder, may be applied to the mat. The binder may beapplied with a curtain coater or a dip and squeeze applicator.

The method may include adding a powdered filler to the bindercomposition. The powdered filler may be added to the binder compositionprior to the application of the binder composition to the wet nonwovenfiber mat. The powdered filler may increase wickability, possibly tocounteract the decreased wickability with the decreased concentration ofmicrofibers. The powdered filler may be hydrophilic and acid-resistant.For example, the powdered filler may be silica, precipitated silica, orsynthetic fumed silica. The powdered filler may be between about 0.1%and about 20% by weight of the nonwoven fiber mat. For example, thepowdered filler may be between about 0.1% and about 10% by weight of thenonwoven fiber mat. The coarse fibers and the microfibers together mayhelp hold the powdered filler in the mixture or slurry or finishednonwoven fiber mat. The filler may be a wetting component.

Examples may further include drying the wet nonwoven fiber mat. Dryingthe cured slurry may include blowing air through the wet nonwoven fibermat. A through-air dryer may dry the cured binder composition and thewet nonwoven fiber mat. Drying may be at temperatures from 250° F. to450° F. or up to 500° F. Drying time may be as little as a few secondsand may not exceed 1 to 2 minutes. Method 500 may exclude drum dryers.Drum dryers may dry conventional nonwoven fiber mats by direct orsubstantially direct contact. In contrast, because of lowerconcentrations of microfibers in these and other methods, air may passthrough the wet nonwoven fiber mat and dry the mat. Sufficient air todry the mat may not be able to pass through a conventional nonwovenfiber mat. Methods may also include vacuuming off excess binder. The wetnonwoven fiber mat may be transported to a moving belt to facilitatedrying.

Method 500 may also include curing the binder composition 504 and thewet nonwoven fiber mat to produce the nonwoven fiber mat. Curing thebinder composition may occur after drying the wet nonwoven fiber mat.Curing the binder composition may result in some chemical reactionsincluding crosslinking reactions but in a lesser amount than thereactions that occur with curing binder compositions for fiberglassinsulation and fiber-reinforced composite applications.

With exposure to 40 wt. % sulfuric acid for 10 minutes conducted usingmethod ISO8787, the nonwoven fiber mat may have an average 40 wt. %sulfuric acid wick height of between about 1 cm and about 5 cm, betweenabout 1 cm and about 4 cm, between about 2 cm and about 4 cm, betweenabout 3 cm and about 4 cm, or between about 4 cm and about 5 cm inexamples. Sulfuric acid used for wicking measurements may have aspecific gravity of 1.28. Water adsorption may be measured by the Cobb₆₀degree. Examples of the present technology may have a Cobb₆₀ degree lessthan one. In other words, the mat adsorbs a weight of water less thanthe weight of the mat. By contrast, conventional AGM pasting papers mayhave Cobb₆₀ degree measurements several times greater than one. Theconventional mats may adsorb a weight of water several times the weightof the mat.

The nonwoven fiber mat may have a total tensile strength greater than 1lbf/in, greater than 5 lbf/in, greater than 10 lbf/in, greater than 15lbf/in, greater than 20 lbf/in, or greater than 25 lbf/in. Tensilestrength may be less than 50 lbf/in. The tensile strengths of nonwovenfiber mats may have a tensile strength many times larger than those ofconventional nonwoven fiber mats. Conventional pasting papers may have abase weight of 0.72 lb/sq and a tensile strength of 2.0 lbf/in (i.e.,6.0 lbf/3 inch). For a 1 inch wide sample, the total tensile strengthnormalized by weight may be greater than 1.0 (lbf/in)/(lb/sq), greaterthan 2.0 (lbf/in)/(lb/sq), greater than 7.0 (lbf/in)/(lb/sq), greaterthan 14.0 (lbf/in)/(lb/sq), greater than 21.0 (lbf/in)/(lb/sq), orgreater than 28.0 (lbf/in)/(lb/sq), for example. For a 3 inch widesample, the total tensile strength normalized by weight may be greaterthan 50 (lbf/3 in)/(lb/sq), greater than 60 (lbf/3 in)/(lb/sq), orgreater than 80 (lbf/3 in)/(lb/sq), or greater than 100 (lbf/3in)/(lb/sq), according to examples. The normalized tensile strength maybe less than 150 (lbf/3 in)/(lb/sq). For the 3 inch wide samples, thenormalized tensile strength units of (lbf/3 in)/(lb/sq) can be dividedby 3 to get units of (lbf/in)/(lb/sq). The sq may be 100 ft².

The mixing, adding, drying operations in methods may be continuousprocesses. These operations may not be batch or semi-batch processes. Inother words, these operations may be run continuously and withoutinterruption. Continuous operation may allow for a faster throughput andmore cost effective operation.

These or other examples of the present technology may include alead-acid battery. The battery may include a positive electrode, anegative electrode, and a nonwoven fiber mat disposed adjacent positiveelectrode or the negative electrode. The nonwoven fiber mat include afirst plurality of first glass fibers having nominal diameters of lessthan 5 μm. The nonwoven fiber mat may further include a second pluralityof second glass fibers having nominal diameters greater than 6 μm. Thefirst plurality of first glass fibers may make up between about 10% andabout 50% by weight of the combined weight of the first plurality offirst glass fibers and the second plurality of second glass fibers. Thefirst plurality of first glass fibers may be any percentage weightdescribed herein. The nonwoven fiber mat may also include a bindercomposition. The nonwoven fiber mat may have an average 40 wt. %sulfuric acid wick height of between about 1 cm and about 5 cm afterexposure to 40 wt. % sulfuric acid for 10 minutes conducted according tomethod ISO8787, while the nonwoven fiber mat may have a total tensilestrength of greater than 2 (lbf/in)/(lb/sq). The nonwoven fiber mat maybe any nonwoven fiber mat described herein. The lead-acid battery mayfurther include a filler. The filler may be precipitated silica,synthetic fumed silica, or any filler described herein.

FIG. 6 shows an example method 600 of making a pasting paper forbattery. Method 600 may include applying acid-resistant bindercomposition to a wet-laid mixture of glass fibers to form a wet nonwovenfiber mat 602. The binder composition may be applied according to any ofthe methods described herein. The mixture of glass fibers may include afirst plurality of microfibers having an average diameter of between 0.5μm and 1.0 μm and a second plurality of coarse fibers having an averagediameter greater than or equal to 8 μm. The mass ratio of the firstplurality of microfibers to the second plurality of coarse fibers may bebetween about 1:5 and about 1:1. The mixture of glass fibers may be anymixture described herein. Method 600 may also include drying the wetnonwoven fiber mat 604. Drying may be carried out by any of the methodsdescribed herein. Method 600 may further include curing theacid-resistant binder composition 606 to produce a pasting paper. Curingmay be accomplished according to any of the methods described herein.The pasting paper may have an average 40 wt. % sulfuric acid wick heightof between about 1 cm and about 5 cm after exposure to 40 wt. % sulfuricacid for 10 minutes conducted according to method ISO8787. In addition,pasting paper may have a total tensile strength of greater than 7(lbf/in)/(lb/sq). The pasting paper may be any nonwoven fiber matdescribed herein.

EXAMPLE 1

Nonwoven glass mat samples were made with a wet-laid machine. Processwater with pH greater than 5 was used. The following Johns Manvilleglass fibers were used: K249T with a nominal fiber diameter of about 13μm and a length of ¾ inch; 206-253 with a nominal fiber diameter ofabout 0.765 μm; 210X-253 with a nominal fiber diameter of about 3.0 μm;and 8 μm/8 mm C glass with a nominal fiber diameter of about 8 μm and alength of 8 mm. The compositions of the nonwoven fiber mats are shown inTable 1.

Air permeability was measured by the Frazier test, which is described byASTM Standard Method D737. This test was usually carried out at adifferential pressure of about 0.5 inches of water. Wicking strength perlength or capillary rise was determined by ISO8787, with the wickingmedium being 40 wt. % sulfuric acid. Thickness was measured with a gaugeunder pressure of 1.868 kPa or 10 kPa. Tensile strength of a 1 inch widesample was measured using an ASTM method by an Instron machine. Tensilestrength was measured in the machine direction (MD) and thecross-machine direction (CMD). The performance of the nonwoven fibermats is shown in Table 2.

TABLE 1 Nonwoven fiber mat properties Mat Sample Weight Coarse ID(lb/sq) LOI Microfiber % Fiber Microfiber A 0.7 10% 50 K249T 206-253 B0.7 20% 50 K249T 206-253 C 0.7 5% 40 K249T 206-253 D 0.7 10% 40 K249T206-253 E 0.7 20% 40 K249T 206-253 F 0.7 10% 30 K249T 206-253 G 0.7 20%30 K249T 206-253 H 0.5 5% 40 K249T 206-253 I 0.5 10% 40 K249T 206-253 J0.5 20% 40 K249T 206-253 K 0.5 10% 30 K249T 206-253 L 0.5 20% 30 K249T206-253 M 0.7 10% 50 8 um/8 mmC 210X-253 N 0.7 10% 80 8 um/8 mmC210X-253 O 0.7 10% 50 K249T 210X-253 P 0.7 10% 80 K249T 210X-253

TABLE 2 Nonwoven glass mat performance characteristics Total tensileAve. Ave. Ave. strength Thickness Ave. Wicking Wicking Ave. normalizedAve. Air under Thickness Length Length Ave. MD CMD by weight Sample Perm1.686 kPa under 10 at 10 at 1 hr Tensile Tensile [(lbf/in)/ ID (cfm/ft²)(mil) kPa (mil) min. (cm) (cm) (lbf/in) (lbf/in) (lb/sq)] A 69.7 13.85.0 2.3 4.55 0.73 0.85 2.26 B 63.4 17.3 6.3 1.55 3.65 2.03 2.7 6.76 C60.2 13.75 4.9 2.0 4.2 0.33 0.3 0.90 D 115 13.95 5.6 1.6 3.15 1.1 1.253.36 E 116.7 14.85 6.1 0.8 1.95 2.53 2.82 7.64 F 144.1 13.7 6.1 1.2 2.651.86 2.36 6.03 G 208.5 13.5 7.0 0.3 0.8 5.2 5.18 14.8 H 131.8 11.2 4.00.9 2.9 0.19 0.22 0.82 I 171.5 11.75 4.2 0.45 1.25 1.0 1.33 4.66 J 304.311.05 4.0 0.3 1.5 2.2 3.8 12 K 325.7 10.35 4.1 0.2 0.45 1.31 1.85 6.32 L435.6 9.55 4.5 0.5 1.0 2.73 4.27 14 M 398.5 10.1 3.9 0.3 0.7 0.57 0.481.50 N 350.0 12.15 4.5 0.35 0.55 0.58 0.55 1.61 O 567.8 12.9 5.2 0.30.55 1.27 2.33 5.14 P 382.3 14.15 5.0 0.4 0.55 0.62 0.98 2.29

When the percentage of microfiber increases from 30% to 50%, especiallyfor microfiber 206-253, the processing difficulty increases. A nonwovenglass mat with 206-253 at 50% and LOI at 10% is challenging to processbecause of lower strength of the mat. When the concentration of themicrofibers is too high, pulling the mat off the formation belt may bedifficult. During removal of the mat, the mat may break as a result ofits low wet web strength.

EXAMPLE 2

Nonwoven glass mat samples were made with a wet-laid machine. Processwater with pH greater than 5 was used. The following Johns Manvilleglass fibers were used: K249T with a nominal fiber diameter of about 13μm and a length of ¾ inch; and 206-253 with a nominal fiber diameter ofabout 0.765 μm.

Air permeability was measured by the TEXTEST™ FX 3300 according to ASTMStandard Method D737. This test was usually carried out at adifferential pressure of about 0.5 inches of water (125 Pa). Wickingstrength per length or capillary rise was determined by ISO8787, withthe wicking medium being 40 wt. % sulfuric acid. Thickness was measuredwith a gauge under pressure of 10 kPa. Tensile strength of a 3 inch widesample was measured using an ASTM method by an Instron machine.

Table 3 shows the compositions of nonwoven fiber mats along withresults. Total tensile strength is normalized by the weight of the mat.The normalized tensile strength is significantly higher for samples inthis example than in Example 1, primarily a result of a higher baseweight.

TABLE 3 Nonwoven fiber mat properties Total tensile strength WickingThickness normalized K249T/ Base Air MD CD length (mil) by weight206-253 LOI wt. perm Tensile Tensile @1 hr @10 [(lbf/in)/ ratio (%)(lb/sq) (cfm) (lbf/3″) (lbf/3″) (cm) kPa (lb/sq)] 90/10 26.4 1.17 300 8046 0.9 11 36 80/20 18.7 1.14 183 45.4 25.9 3.5 9.7 21 80/20 14.7 1.16176 39.4 17.5 3.9 8.9 16 80/20 19.5 1.18 158 53.1 26.5 4.4 9.5 22 75/2517.6 1.12 101 43.6 16 4.6 7.6 18 75/25 18.1 1.21 105 47 18.9 4.9 9.7 1875/25 19.8 1.14 114 45.3 20.4 4.8 8.4 19

EXAMPLE 3

Samples were measured for their Cobb₆₀ degree as an indication of theirhydrophilic or wickability properties. The following Johns Manvilleglass fibers were used: K249T with a nominal fiber diameter of about 13μm and a length of ¾ inch; and 206-253 with a nominal fiber diameter ofabout 0.765 μm. In these experiments, a 1.1 lb/sq mat with 75% K249T and25% 206-253 with 20% LOI were used. Both sides of samples—the binderrich side and the wire side—were measured. The results are shown inTables 4 and 5.

TABLE 4 Binder-rich side Cobb₆₀ degree Absorded amount Absorded amountSample Absorded amount (g) (g/m²) (g water/g mat) 1 0.42 42 0.78 2 0.4545 0.84 3 0.38 38 0.71 4 0.37 37 0.69 5 0.37 37 0.69 6 0.35 35 0.65 70.37 37 0.69 Average 0.39 38.71 0.72 Std. Dev. 0.03 3.50 0.07

TABLE 5 Wire side Cobb₆₀ degree Absorded amount Absorded amount SampleAbsorded amount (g) (g/m²) (g water/g mat) 1 0.43 43 0.80 2 0.47 47 0.883 0.41 41 0.76 4 0.41 41 0.76 5 0.45 45 0.84 6 0.45 45 0.84 7 0.39 390.73 Average 0.43 43.00 0.80 Std. Dev. 0.03 2.83 0.05

With all samples tested, the Cobb₆₀ degree is less than 1. This meansthat the sample adsorbs a weight of water less than or equal to theweight of the mat.

EXAMPLE 4

Nonwoven glass mat samples were made with a wet-laid machine, withprocess water with a pH greater than 5. The following Johns Manvilleglass fibers were used: K249T with a nominal fiber diameter of about 13μm and a length of ¾ inch; and 206-253 with a nominal fiber diameter ofabout 0.765 μm. Silica (Hi-Sil 233 from PPG Industries) was also added.Results are shown in Table 6. Increasing the silica amount increases thewicking length.

TABLE 6 Wicking length with silica Wt. % of Wicking Base silica Airlength K249T/206-253 LOI wt. in the perm @10 mins ratio (%) (lb/sq) mat(cfm) (cm) 70/30 20.3 1.11 0 77 1.1 70/30 23 1.45 12.7 11 4.4 70/30 25.91.16 15.3 3.2 4.3

In the preceding description, for the purposes of explanation, numerousdetails have been set forth in order to provide an understanding ofvarious examples of the present technology. It will be apparent to oneskilled in the art, however, that certain examples may be practicedwithout some of these details, or with additional details.

Having described several examples, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of theinvention. Additionally, a number of well-known processes and elementshave not been described in order to avoid unnecessarily obscuring thepresent invention. Additionally, details of any specific example may notalways be present in variations of that example or may be added to otherexamples.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassed.The upper and lower limits of these smaller ranges may independently beincluded or excluded in the range, and each range where either, neither,or both limits are included in the smaller ranges is also encompassedwithin the invention, subject to any specifically excluded limit in thestated range. Where the stated range includes one or both of the limits,ranges excluding either or both of those included limits are alsoincluded.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise. Thus, for example, reference to “a method” includes aplurality of such methods and reference to “the glass fiber” includesreference to one or more glass fibers and equivalents thereof known tothose skilled in the art, and so forth. The invention has now beendescribed in detail for the purposes of clarity and understanding.However, it will be appreciated that certain changes and modificationsmay be practice within the scope of the appended claims.

Also, the words “comprise,” “comprising,” “include,” “including,” and“includes” when used in this specification and in the following claimsare intended to specify the presence of stated features, integers,components, or steps, but they do not preclude the presence or additionof one or more other features, integers, components, steps, acts, orgroups.

What is claimed is:
 1. A method of making a nonwoven fiber mat for usein a lead-acid battery, the method comprising: mixing a first pluralityof first glass fibers and a second plurality of second glass fibers toform a slurry, maintaining a pH of the slurry at about 5 or higher;removing water from the slurry to form a wet nonwoven fiber mat; addinga binder composition to the wet nonwoven fiber mat, wherein: the wetnonwoven fiber mat comprises the first plurality of first glass fibersand the second plurality of second glass fibers, the first plurality offirst glass fibers has nominal diameters of less than 5 μm, the secondplurality of second glass fibers has nominal diameters of greater than 6μm, and the first plurality of first glass fibers comprises betweenabout 10% and about 50% by weight of the combined weight of the firstplurality of first glass fibers and the second plurality of second glassfibers; and curing the binder composition to produce the nonwoven fibermat, wherein: the nonwoven fiber mat has a Cobb₆₀ degree of less than 1,and the nonwoven fiber mat has a total normalized tensile strength ofgreater than 2 (lbf/in)/(lb/sq).
 2. The method of claim 1, wherein thefirst plurality of first glass fibers has an average diameter of between0.5 μm and 1.0 μm.
 3. The method of claim 1, wherein the first pluralityof first glass fibers has an average diameter of about 0.7 μm.
 4. Themethod of claim 1, wherein the first plurality of first glass fiberscomprises between about 30% and about 40% by weight of the combinedweight of the first plurality of first glass fibers and the secondplurality of second glass fibers.
 5. The method of claim 1, wherein thefirst plurality of first glass fibers comprises between about 40% andabout 50% by weight of the combined weight of the first plurality offirst glass fibers and the second plurality of second glass fibers. 6.The method of claim 1, wherein the first plurality of first glass fiberscomprises between about 20% and about 30% by weight of the combinedweight of the first plurality of first glass fibers and the secondplurality of second glass fibers.
 7. The method of claim 1, wherein thefirst plurality of first glass fibers comprises between about 10% andabout 20% by weight of the combined weight of the first plurality offirst glass fibers and the second plurality of second glass fibers. 8.The method of claim 1, wherein the second plurality of second glassfibers has an average diameter of between about 8 μm and about 13 μm. 9.The method of claim 1, wherein: the first glass fibers comprise a firstglass compound, the second glass fibers comprise a second glasscompound, and the first glass compound is different from the secondglass compound.
 10. The method of claim 1, wherein the method furthercomprises: mixing the first plurality of first glass fibers and thesecond plurality of second glass fibers to form a slurry prior to addingthe binder composition, and maintaining a pH of the slurry at betweenabout 7 and about 8.5.
 11. The method of claim 1, wherein the bindercomposition comprises a powdered filler.
 12. The method of claim 11,wherein the powdered filler is hydrophilic and acid-resistant.
 13. Themethod of claim 11, wherein the powdered filler comprises between about0.1% and about 20% by weight of the nonwoven fiber mat.
 14. The methodof claim 11, wherein the powdered filler is precipitated silica.
 15. Themethod of claim 1, wherein the method further comprises blowing airthrough the wet nonwoven fiber mat.
 16. The method of claim 1, whereinthe nonwoven fiber mat has an average 40 wt. % sulfuric acid wick heightof between about 2 cm and about 4 cm after exposure to 40 wt. % sulfuricacid for 10 minutes conducted according to method ISO8787.
 17. Themethod of claim 1, wherein the nonwoven fiber mat has a total normalizedtensile strength of greater than 7 (lbf/in)/(lb/sq).
 18. The method ofclaim 1, wherein the nonwoven fiber mat has a total normalized tensilestrength of greater than 14 (lbf/in)/(lb/sq).
 19. The method of claim 1,wherein the nonwoven fiber mat has a total normalized tensile strengthof greater than 28 (lbf/in)/(lb/sq).
 20. The method of claim 1, whereinthe method further comprises: drying the wet nonwoven fiber mat, whereinthe mixing, adding, and drying operations are continuous processes. 21.A method of making a pasting paper for a battery, the method comprising:applying an acid-resistant binder composition to a wet-laid mixture ofglass fibers to form a wet nonwoven fiber mat, wherein: the mixture ofglass fibers comprises a first plurality of microfibers having anaverage diameter of between 0.5 μm and 1.0 μm, the mixture of glassfibers comprises a second plurality of coarse fibers having an averagediameter greater than or equal to 8 μm, and the mass ratio of the firstplurality of microfibers to the second plurality of coarse fibers isbetween about 1:5 and about 1:1; drying the wet nonwoven fiber mat; andcuring the acid-resistant binder composition to produce a pasting paper,wherein: the pasting paper has a Cobb₆₀ degree of less than 1, and thepasting paper has a total normalized tensile strength of greater than 7(lbf/in)/(lb/sq).
 22. The method of claim 1, wherein the nonwoven fibermat has an average 40 wt. % sulfuric acid wick height of between about 1cm and about 5 cm after exposure to 40 wt. % sulfuric acid for 10minutes conducted according to method ISO8787.
 23. The method of claim21, wherein the pasting paper has an average 40 wt. % sulfuric acid wickheight of between about 1 cm and about 5 cm after exposure to 40 wt. %sulfuric acid for 10 minutes conducted according to method ISO8787.